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Date:   Wed, 15 Feb 2023 10:13:56 -0800
From:   Jakub Kicinski <kuba@kernel.org>
To:     Florian Westphal <fw@strlen.de>
Cc:     davem@davemloft.net, netdev@vger.kernel.org, edumazet@google.com,
        pabeni@redhat.com, willemb@google.com
Subject: Re: [RFC] net: skbuff: let struct skb_ext live inside the head
Message-ID: <20230215101356.3b86c451@kernel.org>
In-Reply-To: <20230215094332.GB9908@breakpoint.cc>
References: <20230215034444.482178-1-kuba@kernel.org>
        <20230215094332.GB9908@breakpoint.cc>
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On Wed, 15 Feb 2023 10:43:32 +0100 Florian Westphal wrote:
> I think the cleaner solution would be to move the new extension ids
> into sk_buff itself (at the end, uninitialized data unless used).
> 
> Those extensions would always reside there and not in the slab object.

Do you mean the entire extension? 8B of metadata + (possibly) 32B 
of the key?

> Obviously that only makes sense for extensions where we assume
> that typical workload will require them, which might be a hard call to
> make.

I'm guessing that's the reason why Google is okay with putting the key
in the skb - they know they will use it most of the time. But an
average RHEL user may appreciate the skb growth for an esoteric protocol
to a much smaller extent :(